1. Field of the Invention
The present invention relates to an inspection apparatus for foreign matter and pattern defects which is used in the process of manufacturing semiconductor devices.
2. Description of the Background Art
FIG. 12 is a perspective view of a prior art inspection apparatus for foreign matter and pattern defects which is disclosed in Japanese Patent Application Laid-Open No. P11-51622A (1999).
A foreign matter inspection apparatus 10P comprises an inspection illumination device 20P for directing inspection light (laser light) 21P angularly toward a wafer 1P, and a scattered light detector 34P for detecting resultant scattered light 31P from the wafer 1P under dark field illumination, thereby determining the coordinate position of foreign matter 5P. The foreign matter inspection apparatus 10P further comprises a reflection type illumination device 40P and an image pickup device 45P. The image pickup device 45P photographs the coordinate position of the foreign matter 5P determined by a foreign matter judgement device 35P based on the detection of the scattered light detector 34P under bright field illumination provided by the reflection type illumination device 40P. The foreign matter inspection apparatus 10P extracts a foreign matter image, based on the photograph, and then specifies the size, shape, color, and property of the foreign matter, based on the extracted foreign matter image.
In FIG. 12, the reference character 2P designates a first main surface; 3P designates an orientation flat; 4P designates a pellet; 11P designates a stage device; 12P designates an XY table; 13P designates a xcex8 table; 14P designates a controller; 22P designates a laser light irradiating device; 23P designates a condensing lens; 30P designates a scattered light detecting device; 32P designates an objective lens; 33P designates a relay lens; 41P designates white light; 42P designates a white light irradiating device; 43P designates a half mirror; 44P designates a lens; 46P designates an image processor; 47P designates a comparator; 48P designates a verifier; and 49P designates a classifier.
Foreign matter and defects are of a variety of types. For example, some foreign matter affects yields, and some foreign matter does not affect yields. Some objects look like foreign matter or defects, but actually are, for example, grain patterns such as an elongated grain boundary of an aluminum film and scratches resulting from a chemical-mechanical polishing (CMP) process.
However, the use of the image pickup device 45P for inspection for foreign matter and defects sometimes requires very long time. First, the image pickup device 45P performs focusing and magnifying actions to photograph the surface of the wafer 1P, thereby detecting surface information (a microscope image) from the wafer 1P. Next, the foreign matter inspection apparatus 10P extracts image information regarding foreign matter and defects from the microscope image photographed by the image pickup device 45P to identify foreign matter and defects. If numerous, e.g. thousands of to tens of thousands of, pieces of foreign matter and defects are detected, the above described operations require quite long time and impractical, and it is very difficult to grasp an overview of all of the foreign matter and defects within a predetermined length of time. Additionally, the microscope image is an image of the wafer 1P as viewed from above and shows only the plan configuration of the foreign matter and defects. This makes it difficult to judge whether or not the identified foreign matter and defects affect the yields.
Another method of identifying the foreign matter and defects on the wafer surface uses laser light. Laser light directed onto the wafer and scattered therefrom is detected for detection of surface information from the wafer. This method does not require the focusing and magnifying actions to detect the surface information from the wafer accordingly more quickly than the technique employing the image pickup device 45P. This shortens the time required for inspection for the foreign matter and defects. However, this method is disadvantageous in that the light scattered from a pattern defect, a fine foreign particle and a scratch-type defect is low in intensity, resulting in decreased sensitivity of detection of these defects or, in some cases, failure to detect these defects.
As described above, the method employing the microscope and the method employing the laser light have both advantages and disadvantages and present great difficulties in effectively distinguishing the above-mentioned types of foreign matter and defects from each other, based on the wafer surface information.
According to a first aspect of the present invention, an apparatus for inspecting a semiconductor wafer surface for defects and foreign matter comprises: an optical portion including a microscope illumination optical system for acquiring an image of the semiconductor wafer surface by using microscope illumination to detect the semiconductor wafer surface in the form of a piece of first surface information, and a laser scattering type optical system for detecting scattered laser light from the semiconductor wafer surface by using laser light to detect the semiconductor wafer surface in the form of a piece of second surface information; and an analyzer for detecting a plurality of pieces of defect/foreign matter information from the piece of first surface information and the piece of second surface information to categorize the plurality of pieces of defect/foreign matter information into three modes comprised of a first mode containing pieces of defect/foreign matter information represented only in the piece of first surface information, a second mode containing pieces of defect/foreign matter information represented only in the piece of second surface information, and a third mode containing pieces of defect/foreign matter information represented in both the piece of first surface information and the piece of second surface information.
Preferably, according to a second aspect of the present invention, in the apparatus of the first aspect, the analyzer further categorizes the pieces of defect/foreign matter information contained in the third mode into three modes comprised of a fourth mode containing pieces of defect/foreign matter information in which a first defect/foreign matter size represented in the piece of second surface information is greater than a second defect/foreign matter size represented in the piece of first surface information, a fifth mode containing pieces of defect/foreign matter information in which the first defect/foreign matter size is approximately equal to the second defect/foreign matter size, and a sixth mode containing pieces of defect/foreign matter information in which the first defect/foreign matter size is smaller than the second defect/foreign matter size.
Preferably, according to a third aspect of the present invention, in the apparatus of the second aspect, the analyzer counts the number of pieces of defect/foreign matter information contained in the fourth mode.
According to a fourth aspect of the present invention, an apparatus for inspecting a semiconductor wafer surface for defects and foreign matter comprises: an optical portion for detecting the semiconductor wafer surface in the form of a piece of surface information; and an analyzer for detecting a plurality of pieces of defect/foreign matter information each including a horizontal dimension, a vertical dimension and the area of a defect/foreign matter from the piece of surface information to calculate a predetermined elongation factor indicating a degree to which each defect/foreign matter is elongate from the horizontal dimension, the vertical dimension and the area thereof.
Preferably, according to a fifth aspect of the present invention, in the apparatus of the fourth aspect, the elongation factor equals the area divided by the sum of the horizontal dimension squared and the vertical dimension squared; and the analyzer discriminates pieces of defect/foreign matter information including the elongation factor of less than 0.5 and pieces of defect/foreign matter information including the area of less than a predetermined value from other pieces of defect/foreign matter information.
Preferably, according to a sixth aspect of the present invention, in the apparatus of the fourth aspect, the analyzer excludes pieces of defect/foreign matter information detected by the analyzer and including the elongation factor of less than a predetermined value from subjects of analysis when the semiconductor wafer surface includes a metal film.
Preferably, according to a seventh aspect of the present invention, in the apparatus of the first aspect, the optical portion and the analyzer operate in parallel with each other.
Preferably, according to an eighth aspect of the present invention, in the apparatus of the fifth aspect, the analyzer excludes pieces of defect/foreign matter information detected by the analyzer and including the elongation factor of less than a predetermined value from subjects of analysis when the semiconductor wafer surface includes a metal film.
Preferably, according to a ninth aspect of the present invention, in the apparatus of the fourth aspect, the optical portion and the analyzer operate in parallel with each other.
In accordance with the first aspect of the present invention, since defects/foreign matter is detected by the microscope illumination optical system and/or the laser scattering type optical system, the analyzer can easily categorize all pieces of defect/foreign matter information into the three modes. These modes are used to easily control the quality, process and yield of products.
In accordance with the second aspect of the present invention, the difference in property between the illumination optical system and the laser optical system is utilized to assign the defect/foreign matter information having a high possibility of affecting the yield to the fourth mode, the defect/foreign matter information having a medium-level possibility thereof to the fifth mode, and the defect/foreign matter information having a low possibility thereof to the sixth mode, for example.
In accordance with the third aspect of the present invention, the yield is accurately predicted from the number of pieces of defect/foreign matter information counted by the analyzer.
In accordance with the fourth aspect of the present invention, whether or not the possibility that a defect/foreign matter affects the yield is low is found from the elongation factor of the defect/foreign matter. Thus, the yield is accurately predicted.
In accordance with the fifth aspect of the present invention, elongated defects/foreign matter having a low possibility of affecting the yield or extremely small defects/foreign matter is found. Thus, the yield is more accurately predicted.
In accordance with the sixth aspect of the present invention, even if a large number of grain patterns might be detected as defects/foreign matter when the semiconductor wafer surface includes a metal film, the exclusion of the pieces of defect/foreign matter information including the elongation factor of less than the predetermined value from the subjects of analysis accomplishes accordingly accurate analysis.
In accordance with the seventh aspect of the present invention, the result of the analysis of the semiconductor wafer is obtained immediately after the completion of all operations of the optical portion upon the semiconductor wafer.
In accordance with the eighth aspect of the present invention, even if a large number of grain patterns might be detected as defects/foreign matter when the semiconductor wafer surface includes a metal film, the exclusion of the pieces of defect/foreign matter information including the elongation factor of less than the predetermined value from the subjects of analysis accomplishes accordingly accurate analysis.
In accordance with the ninth aspect of the present invention, the result of the analysis of the semiconductor wafer is obtained immediately after the completion of all operations of the optical portion upon the semiconductor wafer.
It is therefore an object of the present invention to provide an inspection apparatus for foreign matter and pattern defects which is capable of easily distinguishing the types of foreign matter and defects from each other.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.